1. Field of the Invention
This invention generally relates to a vehicular anti-theft system, and especially to a vehicular anti-theft system to prevent a vehicle from being stolen by using a password code unique to each vehicle.
2. Related Art
Recently, a vehicular anti-theft system, in which a password code comparison is executed between a password code of an electronic ignition key (hereinafter, called "ignition key") and a password code registered in a vehicle, and then an operation of an engine is detected whether it should be continued or not based on a comparison result when the password code comparison completes, is proposed. In this vehicular anti-theft system a start-up of the engine proceeds until the code comparison completes to prevent decreased startability of the engine.
In the above-mentioned vehicular anti-theft system, the start-up of the engine proceeds during the password code comparison by an ECU (Electronic Control Unit), when an ignition switch is turned on at the time of starting the vehicle. Therefore, the vehicle may be moved until the code comparison completes. That is, even when an unjust operation in which, for example, the ignition switch is turned on and the password code comparison of the ECU is repeated, the vehicle may be repeatedly moved for a short distance.
Furthermore, at the time the engine starts up, when a power supply to the ECU is repeatedly connected and disconnected, an anti-theft communication may be repeatedly performed, and then the password code for anti-theft may be repeatedly sent onto a communication line. Therefore, the password code may be easily collected from the communication line, that is, the password code may be easily stolen.